Thanks, again, for your great comments, Smalma.
As I understand it, there is a basic difference between managing using s/r models with MSH and managing for something like carrying capacity.
That difference is likely along the lines of what is most "productive". Productivity, as I'm using it here, is defined as the amount of future adults produced by current spawners, calculated as a percentage. This is very much your expertise, so let me see if I have it straight. None of this includes the tribal harvest component, if it is a river with tribal harvest.
If we have X numbers returning, and X is, say 60% of carrying capacity, the productivity will be very high. If X is 6000 fish, they will produce something along the lines of 8000 returning adults. If we harvest 2000, then under average conditions, the 6000 left to spawn will produce 8000 again, and we can harvest 2000, etc., etc...
Productivity is pretty high, with each year's run producing 133% of itself. Harvest numbers are consistent. These assumptions are the underpinnings of MSH/MSY.
If we were managing at, say, 75% capacity, we would have 7500 adults returning, who would produce something like 9000 returning adults. Productivity is lower, with returns somewhere along the line of 120%. We'd have that lower productivity and we'd only harvest 1500, rather than 2000.
If we managed at capacity, we'd have 10,000 return, they'd produce 10,000 adults, and productivity would be the lowest, at 1:1.
While I'm making up the exact numbers, do I have the concept correct?
If I do, then we have three choices:
1. Highest productivity, highest harvest, and the least amount of fish in the river.
2. Mid-level productivity, lower harvest, and considerably more fish in the river.
3. Lowest productivity, little or no harvest, and a lot more fish in the river. (Harvest is only due to incidental mortality and poaching).
These are my opinions about those choices:
1. While we have the opportunity to harvest more fish, we have less opportunity to actually encounter any on the river, nearly half the chance of #3. Less encounters equals less opportunity.
Additionally, a poor return for any number of reasons, whether they be inaccurately measured or unanticipated, reduces the opprtunity much more quickly, and fish are harvested further reducing the amount of fish spawning.
2. There are less fish to harvest, but harvest opportunity is still pretty high. Encounters increase by another 20% from #1, so opportunity is somewhat increased, but not significantly.
Again, poor returns may take a larger amount of the needed spawners, be it weather, ocean conditions, whatever. Harvest is taking place without knowing what those other bad effects might be until after harvest takes place.
3. No directed harvest. Encounters are now 167% of what they were at #1. Seasons are longer, more rivers are open, and unanticipated poor runs are less likely to create really poor recruitment. Even if they cause an actual run that is 60% or 70% of predicted, there is no directed harvest to further reduce those numbers, and those numbers will have very high productivity, likely returning to 100% again within two or four years.
The additional opportunity and reduced chance of overfishing under #3 is still based on the s/r models we use now, and with no in-season assessments. If raw data, models, and in-season assessments are improved, it just gets better and better from there.
Another bonus of #3's longer seasons with more open rivers is that since budgetary concerns render enforcement nearly quadrapalegic when they try to do their job, there are more eyes on the river to keep the poachers more under surveillance. On a river that's closed, the only ones there are the poachers...
My final opinion on number 3:
1. More rivers open, longer seasons, and more fish in the rivers.
2. More fishermen days, equalling more money spent on gear, tackle, vehicles, boats, guides, gas, food, lodging, etc., etc.,...
3. A much better chance that I'll be able to take my grandkids steelhead fishing with me (assuming I have some. I'll have to have some kids, first
)
As noted above, these options work even with the same models we use now. So far as choosing between existing models or creating new ones, that's outside my personal expertise. There are WSC bios that have been and continue to research the possibilities.
When are you going to come to another WSC meeting? It looks like we're going to have Dr. Pess come and talk about the preliminary results of the log jam engineering on the Stilly on Wednesday. We'd all benefit from your attendance and comments.
Thanks for the opportunity to have such a good sharing of perspectives and opinions.
Fish on...
Todd.